Auxiliary lighting system

ABSTRACT

An auxiliary lighting system which is particularly adapted for use in lighting an elevator in the event of a main power failure, the system including an emergency or auxiliary source of energy for feeding a lamp load through a transistor control circuit, the transistor control circuit responding to the failure of the main power supply and various conditions of the auxiliary source including full charge, normal discharge and over discharge conditions. The purpose of the foregoing abstract is to enable the Patent Office and the public generally, and especially the scientists, engineers or practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The abstract is neither intended to define the invention of the application, which is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.

United States Patent [19] Edwards 8 Apr. 30, 1974 AUXILIARY LIGHTING SYSTEM [75] Inventor: Franklin R. Edwards, Paoli, Pa.

[73] Assignee: Nylube Products Company, Detroit,

Mich.

22 Filed: Sept. 23, 1971 21 Appl. No.: 183,236

Related US. Application Data [63] Continuation of Ser. No. 809,770, March 24, 1969,

abandoned.

[52] US. Cl 315/86, 307/64, 315/92 [51] Int. Cl. H05b 39/10 [58] Field of Search 307/64; 315/52, 92, 184,

[56] References Cited UNITED STATES PATENTS 3,189,788 6/1965 Cady 307/64 X Primary Examirter-Herman Karl Saalbach Assistant ExaminerLawrence J. Dahl Attorney, Agent, or FirmHamess, Dickey and Pierce [57] ABSTRACT An auxiliary lighting system which is particularly adapted for use in lighting an elevator in the event of a main power failure, the system including an emergency or auxiliary source of energy for feeding a lamp load through a transistor control circuit, the transistor control circuit responding to the failure of the main power supply and various conditions of the auxiliary source including full charge, normal discharge and over discharge conditions.

The purpose of the foregoing abstract is to enable the Patent Office and the public generally, and especially the scientists, engineers or practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The abstract is neither intended to define the invention of the application, which is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.

7 Claims, 1 Drawing Figure 1 AUXILIARY LIGHTING SYSTEM This is a continuation of Ser. No. 809,770, filed Mar. 24, 1969, now abandoned.

BACKGROUND AND SUMMARY OF THE INVENTION This invention relates generally to an auxiliary power system, and more specifically to an auxiliary power system which is adapted to supply electrical energy to an emergency light mounted within an elevator cab, the emergency powersystem supplying energy for lighting when the main power system fails.

The prospects of people becoming trapped on a stalled elevator without illumination due to a power failure has been a cause of concern for a large number of people. This concern was brought to the general public interest in the past few years when great numbers of people were trapped in elevators during widespread area power failures which have occurred. Accordingly, interest has developed in an automatic system for providing illumination of an elevator cab from an auxiliary battery source when the elevator cab is stalled and in complete darkness.

The system of the present invention has been designed as a fully automatic, battery operated, auxiliary lighting system which is adapted to provide illumination of an elevator cab when the main power source for the cab has failed. The novel system is adapted to automatically monitor the main power input to the elevator cab and, upon sensing an interruption of the main power source, immediately provide illumination of the control panel within the elevator cab. In this way, the control station for the cab is lighted to permit the occupants to read emergency instructions for operating the elevator or seek outside help.

Further, the system of the present invention is capable of sensing an over discharge of the battery to disconnect the battery from the emergency lighting load, thus precluding destruction of the battery due to an extreme discharge condition. Also, the system is capable of sensing degrees of discharge of the battery to use a fast recharge when the battery has been discharged by more than a preselected amount. When the battery voltage rises to a selected amount, the battery is then brought up to and maintained in a charged condition with a trickle charge from the main power source. In.

this way, the battery life is further prolonged.

With the system of the present invention, in the event that successive power failures occur before the battery has reached full recharge, the monitoring circuits. are capable of interrupting the charging of the battery and placing the auxiliary batteries in circuit with the emergency lighting system to provide the desired illumination. Further, the system of the present invention is capable of directing current flow through the lamp load when the batteries are being recharged to permit a small current flow through the lamp filaments to indicate to the elevator operator or serviceman that the system is fully charged and operative. The system is also provided with a means for simulating a power failure to permit a complete check of all circuit functions.

Accordingly, it is one object of the present invention to provide an improved auxiliary power system.

It is another object of the present invention to provide an improved power system which is particularly adapted for use in connection with illuminating elevator cabs during emergency conditions.

It is still another object of the present invention to provide an improved auxiliary power source which is capable of monitoring the power input to the elevator cab and provide immediate emergency illumination upon the failure of the main power source.

vIt is another object of the present invention to provide an improved emergency source of electrical energy which includes monitoring circuits to sense an extreme discharge condition in the battery and automatically disconnect the load from the battery;

It is a further object of the present invention to provide an improved auxiliary power system having means for sensing the main input power condition and, immediately upon restoration of the main power, disconnect the auxiliary battery from the load and reconnect the battery to a source of recharging energy.

It is still another object of the present invention to provide an improved auxiliary lighting system for use in connection with an elevator wherein the auxiliary power system is provided with a means for recharging the battery at a first relatively fast charge rate for a preselected portion of the recharging cycle and that a sec- 0nd trickle charge rate to complete the charging cycle and maintain the battery at the fully charged condition.

It is still a further object of the present invention to provide an emergency source of electrical energy for emergency lights which is capable of reconnecting the emergency lights to the auxiliary source during successive failures as long as the battery source is above a preselected level of charge.

It is still a further object of the present invention to provide an improved emergency lighting system which is fed from an auxiliary power source, the system being capable of providing an indication of the operative readiness of the system and the fully charged condition of the battery.

It is still another object of the present invention to provide an improved auxiliary power source foran emergency lighting system which is adapted to be checked through the simulation of a main power failure.

It is still another object of the present invention to provide an improved auxiliary power source for an emergency lighting system which is compact, maintenance free and reliable, inexpensive to manufacture and easy to install.

Further objects, features and advantages of this invention will become apparent from a consideration of the following description, the appended claims and the accompanying drawing in which:

The single FIGURE of the drawing is a schematic diagram illustrating one preferred form of auxiliary power source for an emergency lighting system incorporating the features of the present invention.

Referring now to the drawing, there is illustrated an auxiliary power system 10 for supplying electrical energy'to a lamp load 12 from an emergency power source 14, the source 14 taking the form of a nickelcadmium battery. The battery is adapted to supply energy to the load 12 in the event that the main power source fails, the failure being sensed by a transformer 16 interconnected with the main power supply for the I elevator cab. Also, the transfonner 16 supplies electrical energy to recharge the battery 14 after use and also to provide a limited illumination of the lamps 12 when the system is in the recharge state and generally operatwe. I

Specifically, the transformer 16 includes a primary winding 20 which is magnetically coupled to a secondary winding 22 through a magnetic core element 24. The energy supplied to the secondary winding 22 is used to charge the battery 14 through a rectifying diode 28, current limiting resistor and conductors 32, 34.

' Thus, the batterys voltage depleted and the main power source on, charging current will flow from the secondary winding 22 through the diode 28, resistor 30, and conductor 32, through the battery 14 and back to the secondary winding 22 by means of the conductor 34.

The current through the load circuit 12 is controlled by means of a main power transistor 38 connectedin series with the load 12 and in shunt with the battery 14.

The transistor 38 is controlled by means of a driver transistor 40 connectedlto the base electrode of transistor 38 by means of a resistor 42. The driver transistor 40, in the normal regulating operation, is controlled by means of a potentiometer 46 and resistor 48 combination which forms a voltage divider circuit across the conductors 32, 34. The base electrode of the transistor- 40 is interconnected with the junction point or node 49 between the potentiometer 46 and resistor 48.

As will be explained hereinafter, the cutoff point for transistor 40in the extreme discharge condition is controlled by means of a bridge circuit which includes potentiometer 46 and resistor 48 and also includes a second potentiometer 50, a variable impedence in the form of a diode 52 and a second resistor 54, the diode 52 introducing a hysteresis effect in the circuit. The emitter electrode of transistor 40 is connected to the junction between the potentiometer and the diode 52, it being seen that this latter junction point varies as a nonlinear function of the voltage drop across conductors 32, 34 due to the variation of battery voltage from full voltage and the junction 49 varies as a linear function of the voltage across conductors 32, 34. The parameters of the bridge circuit 64 are selected such that the voltages at nodes 49 and 60 cross over to cut off the transistor 40 at a preselected voltage across conductors 32,34. This operation will be more fully explained in connection with the over-discharge mode of operation of the system.

A diode 68 and resistor 70, and the resistor 54 also form a voltage divider circuit connected across the secondary winding 22 of the transformer 16, the node 74 between resistors and 54 creating a direct current bias for the amplifier circuit described above, including transistors 38 and 40. A first and second capacitor 78 and 80 are provided to filter the rectified voltage being fed to the various subsystems of the control circuit. The load circuit 12 includes a first and second lamp 82 and 84 which are connected in parallel to illuminate the elevator cab when supplied with energy. in the event that one of the lamps burns out or is open-circuited, the other lamp will glow more brightly due to the fact that the entire load current flows through the single lamp. in this way, an indication of a lamp burnout is provided.

In operation and assuming that the battery 14 is fully charged, wherein the battery 14 is at approximately rated voltage or 6 volts, a reduced current flows from the transformer secondary through the diode 28, resistor 30, conductor 32, battery 14 and conductor 34 to maintain the battery at small trickle charge to the battery. Also, a current flows through potentiometer 50, diode 52, and resistor 54 to the other side of the transformer secondary winding 22 and a smaller current flows through potentiometer 46, resistor 48 to the conductor 34. The parameters of these latter circuits are chosen such that the node 49 is at a higher potential than the node 60 tov forward bias the base-emitter junction of transistor 40 to a slight degree. The forward biasing of transistor 40 causes transistor 38 to conduct, thus permitting a small current to flow in the load circuit, including. lamps 82, 84. This current is sufficient to slightly illuminate lamps 82, 84 to provide an indica tion that the circuit is operative and the battery is fully charged. A current also flows in a circuit including the diode 68 and the resistors 70, 54 to provide a bias voltage at node 74. However, the bias voltage is sufficiently low to forward bias the'diode 52 and permit current to flow from the collector-emitter circuit of transistor 80 and the. potentiometer 50. The above noted trickle charge flowing through the battery 14 is sufficient-to maintain the battery 14 fully charged.

When an emergency condition is sensed, that is, the transformer 16 fails to supply a current to the battery 14, the battery then starts supplying energy to the biasing, the controland the load circuits. Thus, the current flows from the battery 14 through the bridge circuit, including the first voltage divider circuit containing potentiometer 46 and resistor 48, and the second voltage divider circuit including potentiometer 50, diode 52 and resistor 54. With these circuits energized, the transistor 40 is rendered conductive thereby causing the transistor 38 to also conduct. The conduction of transistors 40 and 38 is such as to permit a relatively large current, the normal standby current, to flow in the circuit including the emitter-collector circuit of transistor 38 and the load circuit including bulbs 82, 84. In this way, the bulbs are brightly illuminated to illuminate the elevator cab. Of course, the diodes 28 and 68 are back-biased to preclude current flow in the circuit including secondary winding 22.

As current is supplied from the battery to the load circuit 12, the battery starts to deteriorate and the terminal voltage thereof starts to decrease. The decrease in voltage of the battery is sensed by the bridge circuit including the two linear arms of potentiometer 46 and resistor 48 and the nonlinear arm including potentiometer 50, diode element 52 and resistor element 54.

. With the system of the present invention, the parameters are selected such that the voltage at node 60 in accordance with a curve having a lesser slope than the curves describing the decrease in voltage at node 49. The parameters are further selected such that the voltages decrease to cross over at approximately 3 to 3.2 volts thereby rendering transistor 40 nonconductive.

Of course, the nonconduction of transistor 40 cuts ofi transistor 38 reducing the drain from the battery by providing a high impedance to the load circuit 12. The nonconduction of transistors 38, 40 decreases the drain from the'battery 14 to approximately one-fifteenth, of that flowing when the circuit is fully operative and supplying emergency illumination. This latter small current is utilized to maintain transistor 40 in the nonconductive state by means of the current flowing in potentiometers 46, 50 and resistors 48, 54. This condition of supplying the cutoff current will be maintained until such time as the battery voltage drops to zero or the mainpower source is returned to commence charging of thebattery 14.

When the main power source returns to operation, current is again supplied through the transistor 16 to recharge the battery 14. In this situation, the current flows through diode 28 and resistor 30 to the battery 14 to bring the battery 14 up to maximum charge. The rate of charging is approximately the -hour rate, whereby maximum voltage will be returned in approximately 10 hours. Under these circumstances, the transistors 38 and 40 are rendered nonconductive due to the biasing of the base electrode by means of the voltage at node 49. Current also flows in the circuit including diode 68 and resistors 70, 54 to provide a direct current biasing voltage at the node 74. The capacitors 78, 80 filter this rectified alternating current voltage to provide a relatively smooth direct current voltage. When the battery has reached approximately full or rated voltage, the charging current drops to the trickle charge rate as described above.

While the above circuit may be substantially modified to further simplify the circuit, as for example by replacing resistors 70 and 54 by a voltage divider as is the case with potentiometer 46 and resistor 48 to provide low voltage AC or rectified DC. Also, the circuit could be modified to supply main lighting from the load 12 even when the main power is being supplied. Following is a table of circuit parameters which may be selected in providing a system of the presentinvention.

Diodes 28 and 68 are IN 3253 Diode 52 is a l N 914 Transistor 38 is a 2 N 554 Transistor 40 is a 2N 3394 Resistor is 2 OHMS Resistor 42 is 220 OHMS Potentiometer 46 is set at 1000 OHMS Resistor 48 is 3000 OHMS Potentiometer 50 is set at 100 OHMS Resistor 54 is 100 OHMS Resistor 70 is 220 OHMS Capacitor 78 and 80 are approximately 50 microfarads.

While it will be apparent that the embodiment of the invention herein disclosed is well calculated to fulfill the objects of the invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. An auxiliary power supply for a lighting system for supplying electrical energy to a lamp load when the main power supply fails comprising an auxiliary source of energy and control circuit means connected in controlling relation with the main supply, the lamp load and said auxiliary source, said control circuit means including a controlled element in circuit with the lamp load and a bridge bias circuit connected to control the conduction of the controlled element in response to the functioning of the main power supply and the voltage condition of the auxiliary source, said bridge bias circuit being supplied with energy from the main supply when operative and said auxiliary source when the main supply fails, said control circuit means including a controlling element having a first electrode connected to the controlled element to control the operation of said controlled element and a second and third electrode, said bridge bias circuit having a first terminal connected to said second electrode and a second terminal connected to said third electrode, said bridge bias circuit including means for providing hysteresis action in said bridge biasing circuit so that said first terminal voltage exceeds said second terminal voltage for one mode of operation for said bridge circuit wherein said auxiliary source is provided charging current from said main source and said second terminal voltage exceeds said first terminal voltage for another mode of operation of said bridge circuit, the relative voltages of said first and second terminal controlling the conductive and nonconductive state of said controlling element, said first and second terminal voltages varying depending on whether the bridge bias circuit is fed from the main supply or the auxiliary supply for a given voltage applied to the bridge.

2. The improvement of claim 1 wherein said bridge includes at least one nonlinear variable impedance device for varying the control of the bridge nonlinearly with voltage.

3. The improvement of claim 2 wherein said bridge includes av first voltage divider network forming two arms of said bridge and a second voltage divider network forming a second two arms of said bridge, said controlling element being connected between the midpoints between said first and second arms of said first and second voltage divider networks.

4. The improvement of claim 3 wherein said controlling element is a semiconductor device having two main electrodes and a control electrode, one of said main electrodes being connected to one of said midpoints and said control electrode being connected to the other midpoint, the conduction of said semiconductor device being cut-ofi at a cross-over point in voltage between said midpoints.

5. The improvement of claim 4 wherein said bridge senses the auxiliary source during a period said auxiliary source is supplying energy to the load, said auxiliary source having a voltage dropping characteristic as energy is being supplied to the load, said cut-off occurring at a preselected low voltage point of said auxiliary source.

6. The improvement of claim 1 wherein said auxiliary source is a battery and said main supply supplies charging current to said battery when said battery is below normal voltage and the main supply is operative, said control circuit biasing said controlled element to cause current to flow in said load when said battery is fully charged.

7. The improvement of claim 6 wherein said battery is charged fromthe main supply at a first high rate when said battery is at a low voltage condition and at a trickle charge rate when said battery is approximately at full charge. 

1. An auxiliary power supply for a lighting system for supplying electrical energy to a lamp load when the main power supply fails comprising an auxiliary source of energy and control circuit means connected in controlling relation with the main supply, the lamp load and said auxiliary source, said control circuit means including a controlled element in circuit with the lamp load and a bridge bias circuit connected to control the conduction of the controlled element in response to the functioning of the main power supply and the voltage condition of the auxiliary source, said bridge bias circuit being supplied with energy from the main supply when operative and said auxiliary source when the main supply fails, said control circuit means including a controlling element having a first electrode connected to the controlled element to control the operation of said controlled element and a second and third electrode, said bridge bias circuit having a first terminal connected to said second electrode and a second terminal connected to said third electrode, said bridge bias circuit including means for providing hysteresis action in said bridge biasing circuit so that said first terminal voltage exceeds said second terminal voltage for one mode of operation for said bridge circuit wherein said auxiliary source is provided charging current from said main source and said second terminal voltage exceeds said first terminal voltage for another mode of operation of said bridge circuit, the relative voltages of said first and second terminal controlling the conductive and nonconductive state of said controlling element, said first and second terminal voltages varying depending on whether the bridge bias circuit is fed from the main supply or the auxiliary supply for a given voltage applied to the bridge.
 2. The improvement of claim 1 wherein said bridge includes at least one nonlinear variable impedance device for varying the control of the bridge nonlinearly with voltage.
 3. The improvement of claim 2 wherein said bridge includes a first voltage divider network forming two arms of said bridge and a second voltage divider network forming a second two arms of said bridge, said controlling element being connected between the midpoints between said first and second arms of said first and second voltage divider networks.
 4. The improvement of claim 3 wherein said controlling element is a semiconductor device having two main eleCtrodes and a control electrode, one of said main electrodes being connected to one of said midpoints and said control electrode being connected to the other midpoint, the conduction of said semiconductor device being cut-off at a cross-over point in voltage between said midpoints.
 5. The improvement of claim 4 wherein said bridge senses the auxiliary source during a period said auxiliary source is supplying energy to the load, said auxiliary source having a voltage dropping characteristic as energy is being supplied to the load, said cut-off occurring at a preselected low voltage point of said auxiliary source.
 6. The improvement of claim 1 wherein said auxiliary source is a battery and said main supply supplies charging current to said battery when said battery is below normal voltage and the main supply is operative, said control circuit biasing said controlled element to cause current to flow in said load when said battery is fully charged.
 7. The improvement of claim 6 wherein said battery is charged from the main supply at a first high rate when said battery is at a low voltage condition and at a trickle charge rate when said battery is approximately at full charge. 